1. Field of the Invention
The present invention relates generally to the field of electro-optics and more particularly to apparatus for the detection and spectographic analysis of laser energy.
2. Description of the Prior Art
The prior art in the field to which the present invention relates may be separated into two basic categories; spectral research instruments and field apparatus.
With the increasing significance of spectral research a wide variety of spectrographic instruments have been produced, which generally involve the use of either prisms or diffraction gratings to disperse the incoming radiation. Prisms, however, have very poor linearity of wavelength scale which is uncontrollable and which results in a limitation upon the dynamic range of the instrument. The use of diffraction gratings, on the other hand, introduces an ambiguity due to the overlap of orders of interference which also serves to limit the usable dynamic range of the instrument. Particularly in the field of infrared spectroscopy the detector elements which may be used with the conventional spectrograph are limited due to the low energy which is generally available in the dispersed radiation beam. If maximum sensitivity is needed, spectroscopic apparatus must have high energy throughout for efficiency.
It will be appreciated that there are many instances where it is desirable in a field rather than a laboratory environment to detect laser radiation and to differentiate it from other light sources. Since the conventional spectrograph is typically a delicate, bulky and expensive instrument, its use in a field environment is at least infeasible if not impossible. The alternative apparatus for laser detection in the field has in the past involved the use of a multiplicity of detector elements, each having a narrow bandpass filter corresponding to the wavelengths of lasers with which an encounter may be anticipated. The shortcomings of this approach lie basically in its incapacity to provide for unanticipated wavelengths and its susceptability to false alarms due to naturally occurring phenomena such as solar radiation. Further the use of multiple filtered detectors requires an output lead pair for each detector. If a large spectral range is to be covered the generation of a yes/no indication as to whether the detected radiation is from a laser can thus require apparatus of considerable complexity.